This invention relates to certain substituted 6-amido-2-S-oxides of substituted 2-organothio-pen-2-em-3-carboxylic acids (I) which are useful as antibiotics: ##STR2## wherein: R.sup.1 is H or acyl; R.sup.2 is hydrogen or methoxy; R.sup.3 is alkyl having from 1-6 carbon atoms; phenylalkyl having from 7-12 carbon atoms and cycloalkyl having 3-6 carbon atoms; and R.sup.4 is hydrogen, a removable protecting group, or a pharmaceutically acceptable salt or ester moiety.
Suitable values for R.sup.1 as acyl are disclosed in U.S. Pat. No. 4,226,866, issued Oct. 17, 1980, which is incorporated herein by reference. Generally, R.sup.1 as acyl is chosen from those acyls known to be effective in the penicillin and cephalosporin art. Representative values for R.sup.1 as acyl include: